The radio subsystem (RSS) of a wireless communication network typically comprises base station subsystems (BSS) and mobile stations (MS). A typical base station subsystem includes a base station controller (BSC) and all the base stations (BS) that it controls. The base stations, in turn, communicate with mobile stations such as digital/cellular phones and the like. In wireless communications, an air interface is used for exchanging information between the mobile stations, base stations, base station controllers, and so on. More specifically, the air interface typically comprises a plurality of communication channels for exchanging voice, data, and/or signaling information.
FIG. 1 illustrates an exemplary and well-known radio interface protocol architecture 100 for a typical wireless communication network and, in particular, shows the termination points at the various layers of the protocol. The physical (PHY) layer 101, which is terminated in base station 105 (also commonly referred to as Node-B) provides the functionality for modulation, coding, spreading, and so on for transmissions between base station 105 and mobile station 106. The media access control (MAC) layer 102, which is terminated in base station controller (BSC) 107 (also referred to as radio network controller), provides the multiplexing and medium access control functions. The radio link control (RLC) layer 103, which is also terminated in base station controller 107, provides the well-known automatic repeat request (ARQ) functionality for wireless transmissions. The radio resource control (RRC) layer 104 is also terminated in base station controller 107 and handles the control plane signaling of layer 3 messages between the network and mobile station 106. Layer 3 signaling typically includes, by way of example: system information broadcasting from the network to all mobile stations; establishment, re-establishment, maintenance and release of a radio resource control connection between a mobile station and the network; establishment, reconfiguration and release of radio bearers; assignment, reconfiguration and release of radio resources for the radio resource control connection; measurement signaling; and so on.
In the evolving wireless data systems, such as the well-known 1x-EV-DO and 1xEV-DV standards as well as the High Speed Downlink Packet Access (HSDPA) specification in the Universal Mobile Telecommunication System (UMTS) standard, the scheduling function is moved from base station controller 107 to base station 105 in order to provide “fast” scheduling based on channel quality feedback from the users. Moreover, new technologies such as adaptive modulation and coding (AMC) and hybrid ARQ (HARQ) have also been introduced to improve the overall system capacity. In general, a scheduler selects a user for transmission at a given time and adaptive modulation and coding allows selection of the appropriate transport format (modulation and coding) for the current channel conditions seen by the user.
FIG. 2 shows radio interface protocol architecture 110, which is similar in all respects to that shown in FIG. 1, except that media access control—high speed (MAC-hs) 111 is provided to handle the scheduler, AMC and Hybrid ARQ functions. Because MAC-hs 111 is terminated at base station 105, a fast response time can therefore be realized since base station 105 is closer to mobile station 106 than is base station controller 107. As is well known, MAC-hs 111 manages the data transmitted on the air interface. Moreover, MAC-hs 111 is used to manage the physical resources allocated to High Speed Downlink Packet Access (HSDPA), for example. In general, the functions carried out by MAC-hs 111 include flow control, scheduling/priority handling, Hybrid ARQ, and a physical layer transport format, e.g., modulation, coding scheme, etc. as shown in FIG. 3.
The signaling function in existing wireless architectures and protocols suffer from several disadvantages, namely delay and inefficient resource allocation and usage. In particular, certain signaling and control functions are handled in an indirect manner that adds unnecessary delay to the transmission and uses bandwidth that could otherwise be used more efficiently for other purposes, e.g., for data transmission to mobile stations. For example, FIGS. 4 and 5 illustrate a few exemplary scenarios in which these problems arise. In FIG. 4, for example, signaling between base station 105 and mobile station 106 is carried out via base station controller 107 as shown by signaling message 150 that is first sent from base station 105 to base station controller 107 and then by signaling message 151 that is subsequently sent from base station controller 107 to mobile station 106. This indirect signaling takes place via radio resource control (RRC) layer 104 (FIG. 1). As such, the RRC-based signaling can be slow depending on delays in the network as well as use of longer frames for transmission (e.g., the HSDPA uses 2.0 millisecond frames while the RRC signaling layer 104 uses 10 millisecond or larger frames). Moreover, when a control message related to MAC-hs 111 needs to be transmitted to mobile stations, the information is first sent via MAC-hs 111 in base station 105 to RRC layer 104 in base station controller 107, which then forwards the signaling message to mobile station 106.
FIG. 5 illustrates another disadvantage of the existing transmission schemes. In particular, data transmissions over the air interface are sent separately to each of mobile stations 106 and 160 from base station 105 as shown by transmissions 161-164. Utilizing the resource (i.e., air interface) in this manner is not an efficient use of capacity, especially in the case where the same data or signaling transmission needs to be transmitted to multiple mobile stations (e.g., broadcast, multicast, etc).
Accordingly, the aforementioned signaling and transmission schemes have significant disadvantages in terms of introducing large signaling delays and degradation to system capacity (e.g., resource allocation).